The invention relates to a retrievable subsurface well casing slip and packer apparatus and method. In particular the invention relates to a slip apparatus and method for anchoring a tool within a well casing and a packer apparatus and method for sealing off a well casing with a tubing or production string. The invention further relates to a locking, setting and unsetting mechanism for a slip or packer apparatus and method which is reliable, durable and economical to manufacture.
Retrievable subsurface well casing slip and packer apparatus are well known in the prior art. An example of such a tool is shown in U.S. Pat. No. 3,507,327 issued to D. V. Chenoweth, which is incorporated herein in to by specific reference thereto for all purposes. In practice a slip and packer apparatus is lowered down a well casing to a desired position below the surface and locked with the well casing and packed off to provide a seal. A typical method of doing this is by attaching the slip and packer apparatus to a running or production string which is run down the well casing by connecting joints of tubing which are of lesser diameter than the well casing. A known method of setting the apparatus in position to which this invention relates is the manipulation of a running string to set and pack off a tool and to unset and unpack the tool for removal. This is achieved with the apparatus disclosed in the Chenoweth patent by rotation and vertical movement of the running string which effects setting of the slip apparatus and packing-off of the packing apparatus. In the case of the Chenoweth patent the apparatus is maintained in its locked running-in position by not rotating the tubing string when it is positioned in the well casing until it is desired to set and pack it off. Rotation of the running string in one direction unlocks the Chenoweth apparatus from its non-engaging, locked, running-in position so that continued lowering of the running string will provide for engagement of the slip apparatus to set the tool in a desired position within a well casing. When it is desired to release the Chenoweth tool, the running string is rotated in the same direction which will disengage the packing apparatus and the slip apparatus so that the running string and tool may be removed from the well casing.
During the running-in operation it may be desirable to rotate the running string in both directions to facilitate lowering and positioning in the well casing. Rotation of a running string to which the Chenoweth apparatus is attached in the direction opposite of the unlocking direction and releasing direction may result in jamming of the apparatus which requires removal of the tool from the well casing for resetting.
The Chenoweth patent also discloses a slip apparatus which includes upper and lower slips and a separate interconnecting slip ring which prevents relative longitudinal movement between its upper and lower slips. This requires a separate part for the slip ring which retains upper and lower slips.
It is also known in the prior art to provide a J-slot locking and setting mechanism for a slip and packing apparatus to prevent unlocking of the tool from its running-in position and whereby it can be set and packed off. Examples of retrievable packer systems which use a J-lock are those manufactured by Otis Production Packer Equipment And Services and Dresser-Guilberson. Another example of a packer system which uses a slot and pin is that used by Arrow Oil Tools, Inc. which uses J-pins to allow setting and release of the tool. A disadvantage of a J-slot in setting a tool is that the packer may be over stressed to set the tool in its engaging position.
It is also known to have upper and lower slips which are interconnected without a slip ring. A retrievable packer made by AVA International utilizes a slip system having vertically spaced upper and lower slips which are directly connected to each other. Each upper slip utilizes a key-member which meshes with a T-slot in the lower slip which is directly below the upper slip.
It is an object of the present invention to provide a slip and packer apparatus which may be run into a well casing and whereby the running string may be rotated in either direction during running without release and unlocking of the slip and packing apparatus for setting. It is a further object of the invention to provide a positive locking means for a slip and packer apparatus to prevent accidental unlocking. It is a further object of the invention to provide a slip and packer apparatus which has interconnecting slip means which are directly connected and which provide a circumferential gripping area greater than 360.degree.. It is a further object of the invention to provide a slip and packer apparatus and method which is reliable, durable and economical to manufacture. The apparatus and method of the invention further includes other advantages and additional objects will be apparent from the following detailed disclosure of the preferred embodiment.